The use of heat pumps augmented by a secondary system for collecting and supplying heat thereto for the purpose of heating structures such as buildings has been known in the past. However, the usage of heat pumps has been on a limited basis and primarily in only certain geographical areas where either the average temperature is quite high as, for example, in the south, or in areas where sun energy is plentiful and solar energy systems may be conveniently employed. However, in temperate and colder climates, it has not been as practical to use such techniques. Heat pumps perform very efficiently at outside ambient temperatures of 35.degree., 25.degree., or even 15.degree. F. However, the efficiency of heat pumps drops off after temperatures become lower and at 10.degree. to 15.degree. F. evaporator temperature a heat pump is not very efficient.
The present invention provides structure for collecting heat energy from sources such as the ground, sunshine, ponds, lakes, swimming pools, rivers, wells, and creeks. Heat may also be transferred from such heat reservoirs as masonry or other storage mediums, including off peak storage banks.
The present system for collecting heat for the heat pump departs from past practice in that a refrigerant, such as the fluorinated hydrocarbons, is used as a heat transfer medium. In the system, a heat collector structure is filled with liquid refrigerant, the balance of the system containing refrigerant gas according to the pressure-temperature relationship of the refrigerant. Normally, there are no pressure reducing valves or regulating valves used in the system. The entire system being basically under the same pressure, such control devices may be dispensed with. However, this is not to exclude the use of such structures under certain conditions. The pressure will be determined by the condensing temperature in the heat dissipator.
In the present invention, latent heat of the refrigerant is picked up, causing the liquid refrigerant to "boil" and change to vapor according to the amount of heat picked up. Vapor pressure immediately travels to the heat dissipating device where the refrigerant condenses and returns as a liquid to the heat collecting structure, this being a continuous procedure as long as heat is being absorbed by the heat collecting structure.
Whenever the heat dissipator is located above the heat collecting structure, a circulating pump can usually be eliminated. When desired to locate the heat dissipator below or near the same height as heat pick up, a small refrigerant circulating pump is used. However, since latent heat of the refrigerant is used for heat movement, a relatively small weight of refrigerant needs to be circulated and very little power is required.
The refrigerant charged system is very useful in picking up an abundance of "low grade" heat for use by the heat pump. It is very important to the present invention that considerable amounts of low grade heat may be transferred from the ground, water or other heat storage means for use in heat pumps with the expenditure of very little or no energy.
The use of a refrigerant charged heat collecting system has many advantages as opposed to a heat collecting system employing a liquid which changes temperature upon absorption of heat as opposed to changing from a liquid to a gas. Some of the advantages are listed below:
(1) All concern as to freezing of heat collecting fluid at low temperature is forever eliminated, because the refrigerant does not freeze.
(2) Any question as to chemical action or corrosion in the system is completely eliminated.
(3) Toxicity is not a problem . Most common refrigerants are non-toxic and are used widely with foods.
(4) The refrigerant charged system is more efficient since basically latent heat is used instead of sensible heat as in the case of a liquid which does not become a gas. This also permits more heat to be moved through smaller lines and longer distances without a pump.
(5) In many cases the primary or circulating pump can be eliminated and a very efficient "passive" system can result.
(6) A refrigerant charged system can pick up a large amount of low grade energy for use with heat pumps.
(7) Refrigerants are most readily available. Since the system is never "flooded" only a few pounds of refrigerants are used and cost is low.
(8) Connections can readily be made with copper tubing and flare nuts. Also, copper tubing may be used and all joints "hard soldered". Pipe should not be used. Steel tubing may be used if joints are "hard soldered".
(9) Since the system is not "flooded" and latent heat is involved, check valves are not usually necessary to prevent reverse circulation.
(10) In the refrigerant charged system very small leaks can readily be found with a "Halide" leak detector.
(11) A network of refrigeration service engineers throughout the country already has the basic technology and tools to install and service refrigerant charged systems.